1. Field of the Invention
The present invention relates to charge transport layers useful in organic electronic devices. The invention further relates to electronic devices in which there is at least one such charge transport layer.
2. Background
In organic electronic devices, such as organic light-emitting diodes (“OLEDs”), that make up displays, the organic active layer is sandwiched between two electrical contact layers. In an OLED the organic active layer is photoactive where upon application of a voltage across the electrical contact layers, the contact layers generate positively-charged holes and negatively charged electrons, which combine in the photoactive layer and cause photon generation. At least one of the electrical contact layers is transparent or translucent so that the generated photons can pass through the electrical contact layer and escape the device.
It is well known to use organic electroluminescent compounds as the photoactive component in OLEDs. Simple organic molecules, conjugated polymers, and organometallic complexes have been used.
These devices frequently include one or more charge transport layers, which are positioned between the photoactive (e.g., light-emitting) layer and one or both of the contact layers. A hole transport layer may be positioned between the photoactive layer and the hole-injecting contact layer, also called the anode. An electron transport layer may be positioned between the photoactive layer and the electron-injecting contact layer, also called the cathode.
There is a continuing need for charge transport layers.